1. Field of the Invention
This invention relates to an image recording apparatus which records an image on a recording medium by moving the recording medium and an inkjet head relative to each other.
2. Description of the Related Art
UV (ultraviolet) ink is used in the image recording apparatus which records an image on a recording medium by moving the recording medium and inkjet head relative to each other. The UV ink is also called an ultraviolet curable ink which contains, for example, pigment, a UV curable monomer and photoinitiator. The UV ink hardens by being irradiated with ultraviolet light from a UV lamp immediately after application to the recording medium. Therefore, by using such UV ink, it is possible to perform proper printing not only on ordinary paper, but also on a plastic film or the like which does not absorb ink.
Such UV ink may be white ink or an ink containing metal particles, which encounters a phenomenon of sedimentation in which pigment gathers vertically downward within the ink. When such sedimentation occurs, there is a possibility of causing a reduction in an inside diameter of a pipe due to adhesion of the pigment to inner walls of the pipe, resulting in a reduction in ink flow rate, clogging of the pipe and defective discharge from the inkjet head.
In the inkjet recording apparatus described in Japanese Unexamined Patent Publication No. 2006-327048, therefore, pigment sedimentation is prevented by circulating ink in a circulating pipe with a pump.
Generally, UV ink is highly corrosive. Therefore, the construction described in Japanese Unexamined Patent Publication No. 2006-327048 noted above must use an expensive, corrosion-resistant pump. This poses a problem that the entire apparatus becomes high-priced.